A Clustered Randomized Controlled Trial to Reduce Secondhand Smoke Exposure Among Nonsmoking Pregnant Women in Sichuan Province, China

Introduction: Nonsmoking pregnant women in China have significant exposure to secondhand smoke (SHS). Few interventions have focused on pregnant women reducing their SHS exposure.

Methods: This clustered randomized controlled trial, conducted at eight hospitals in Sichuan, China, compared a prenatal health education intervention with usual clinical care as a control. The primary outcome was self-reported "no SHS exposure" before and 3 months after birth. The intervention consisted of three large group educational sessions, standardized clinician advice, brief monthly follow-up calls, and educational materials and resources. A random sample of participants was biochemically validated before birth with hair nicotine, a long-term biomarker of smoke exposure.

Results: Overall, 1181 participants were randomized to intervention (n = 526) and control (n = 655) groups. More participants in the intervention group than the control group reported no SHS exposure 3 months after birth (Total: 77.9% vs. 52.6%, P < .001; Home: 81.2% vs. 53.3%, P < .001). The intervention group also had greater changes in improved smoke-free homes and SHS knowledge and attitudes. Controlling for covariates, the intervention group was less likely to report SHS exposure than the control group (Total: OR = 0.47, 95% CI = 0.31 to 0.71; Home: OR = 0.33, 95% CI = 0.21 to 0.53), and this effect was sustained 3 months after birth. The adjusted log concentration of hair nicotine for the intervention group decreased by 0.28 log µg/g more than the control group.

Conclusions: Our smoke-free health education intervention for nonsmoking pregnant women significantly reduced SHS exposure before and after birth. This intervention model can become part of a standard protocol for the care of pregnant women in hospital settings.